Methods and apparatus for lapping workpieces



Aug. 19, 1969 3,461,617

METHODS AND APPARATUS FOR LAPPING WORKPIECES D. W. WRIGHT 3 Sheets-$heet1 Filed Aug. 18, 1965 INVENTOR. Da/e W Whig/71 BY QTTORNfiXQ Aug. 19,1969 o. w. WRIGHT 3,461,517

METHODS AND APPARATUS FOR LAPPING WORKPIECES Filed Aug. 18, 1965 5Sheets-Sheet B INVENTQR. Dq/e W. wry/J7 M MVMQW United States Patent '03,461,617 METHODS AND APPARATUS FOR LAPPING WORKPIECES Dale W. Wright,Saginaw, Mich, assignor to Miles Machinery Company, Saginaw, Mich. FiledAug. 18, 1965, Ser. No. 480,574 Int. Cl. B24b 7/02, 9/00 U.S. Cl. 51-12117 Claims ABSTRACT OF THE DISCLOSURE A lapping machine having arotatable, annular lapping wheel and a workpiece support for holding aworkpiece against the wheel, the workpiece support including drivingmeans for rotating the support relatively to the wheel in such mannerthat the workpiece traces a path relative to the wheel which isselectively circular or sinusoidal.

This invention relates to a machine tool construction and moreparticularly to apparatus and methods for lapping workpieces having flatsurfaces.

Lapping machines of the general class to which the invention relateshave been proposed heretofore, but not all of them have been altogethersatisfactory for a number of reasons. For example, some of the knownmachines are so constructed that successive workpieces move relativelyto a lapping wheel in a uniform circular path, thereby rather rapidlyforming a groove in the lapping wheel and necessitating frequentdressing of the wheel. The task of dressing the lapping wheel of some ofthe known machines often requires substantial dismantling of themachines, resulting in considerable loss in the productive use of themachine.

In those machines that are so constructed that each workpiece followsthe identical path with respect to the lapping wheel, the grooving ofthe wheel not only results in the problems stated above, but frequentlycauses the grooving of many workpieces, particularly those workpiecesthat are lapped just prior to dressing of the wheel. Such workpiecesmust either be scrapped or subjected to further lapping operations,either of which is undesirable.

A particularly important object of the invention is to provide lappingapparatus and methods which overcome the disadvantages hereinbeforedescribed.

Another object of the invention is to provide lapping apparatus whichrequires but infrequent dressing of the lapping wheel and wherein thedressing of the wheel may be accomplished rapidly without necessitatingany dismantling of the machine parts.

A further object of the invention is to provide lapping apparatus inwhich the part to be lapped is caused to traverse the lapping wheel in acircuitous path so as to enable each part to be presented to the lappingwheel from a number of different relative positions, thereby providing asmoother or flatter surface finish on the part.

Another object of the invention is to provide lapping apparatus of thecharacter described and in which the path of a part relative to thelapping wheel may be adjusted so as to achieve the optimum movement ofthe part relative to the wheel.

A further object of the invention is to provide lapping apparatuswherein the speed of relative movement between the lapping wheel and thepart to be lapped may be adjusted within wide limits.

Another object of the invention is to provide lapping apparatus whereinthe force by which a part is held against the lapping wheel may beadjusted simply and quickly.

Patented Aug. 19, 1959 Other objects and advantages of the inventionwill be pointed out specifically or will become apparent from thefollowing description when it is considered in conjunction with theappended claims and the accompanying drawings, in which:

FIGURE 1 is a fragmentary view partly in side elevation and partly insection of lapping apparatus constructed in accordance with theinvention;

FIGURE 2 is an enlarged, vertical sectional view taken on the line 2--2of FIGURE 1;

FIGURE 3 is a sectional View taken on the line 33 of FIGURE 2;

FIGURE 4 is an enlarged sectional view taken on the line 44 of FIGURE 2;

FIGURE 5 is a fragmentary, enlarged sectional view of adjustingapparatus forming part of the construction;

FIGURE 6 is a reduced, somewhat diagrammatic, top plan view of theapparatus;

FIGURE 7 is a diagrammatic view of hydraulic apparatus which may beincorporated in the apparatus; and

FIGURE 8 is a fragmentary, enlarged, diagrammatic view illustrating thepath that a typical workpiece may take with respect to a lapping wheel.

Apparatus constructed in accordance with the disclosed embodiment of theinvention is adapted for use in conjunction with a base 1 of anysuitable construction and having a horizontal bed or table 2 that may besupported by means of suitable frame members 3. Fixed on the uppersurface of the bed 2 is a support 4 in which a drum 5 is joumaled bybearings 6 for rotation about a vertical axis. Secured in any suitablemanner to the drum 5 is an annular lapping or grinding wheel 7.

The drum 5 and the wheel 7 are adapted to be rotated by means of anelectric motor 8 that is connected by belts or the like 9 to the inputshaft 10 of a variable speed reduction drive unit 11 of knownconstruction, the output shaft 12 of which may be connected by belts orthe like 13 to a drive shaft 14 that is fixedl to and rotates the drum5, and is journaled in bearings 15 supported in the base 1. Preferably,the wheel 7 is located within a cupshaped shield 16 that is secured tothe bed 2 and which prevents the splashing of coolant. The apparatusdescribed thus far is conventional and forms no part of the inventionper se.

At the rear end of the table 2 is mounted a base or pedestal 17 in whichis fixed an upstanding tubular mounting post 18 (see FIGURES l and 5). Asupporting frame or arm member 19 is mounted at its rear end on the post18 for both axial and rotary movements. A vertical opening 20 isprovided at the forward or free end of the member 19 and the latter hasa flat top wall 22. Bearings 23 and 24 are carried by the arm 19 andaccommodate the mounting member 18 therein. As is best shown in FIG- URE5, the post 18 extends completely through the member 19 and is receivedwithin a cylinder 25 that is fixed to and extends above the top wall 22.The upper end of the cylinder 25 is sealed by a cap 26 which is fixed tothe member 19 by means of bolts 27.

Manually operable means 28 is provided to effect vertical adjustment ofthe member 19 relative to the bases 1 and 17 and comprises a shaft 29having a smooth shank portion 30 that extends through a sealed openingformed in the cap 26 and terminates at its lower end in a threadedportion 31 that is received in the correspondingly threaded bore 32 of aplug 33 which is fixed in the upper end of the mounting member 18. Onthe shank 30 is a flange 34 that bears against a wear ring 35 carried bythe plate 26, and the threaded portion 31 terminates in a reduced endextension 36 on which is secured a thrust ring 37. The upper end of theshaft 29 preferably has a handwheel 38 secured thereto. The constructionand arrangement of the adjusting means 28 are such that rotation of theshaft 29 in one direction will cause the arm 19 to move upwardly axiallyof the mounting member 18, and rotation of the shaft 29 in the oppositedirection will cause the member 19 to move downwardly.

The apparatus also includes power means designated generally by thereference character 40 (FIGURE 7) for effecting vertical movement of themember 19 relative to the base 1. The power means includes a preferablyhydraulic pump 41 that is adapted to pump fluid from a reservoir 42through a line 43 leading to a manually operable valve 44 so as todirect fluids selectively to a return line 45 or to a line 46. The line46 extends through the mounting member 18 and communicates with a port47 (FIG- URE that extends through the plug 33. The arrangement is suchthat, in one position of the valve 44, fluid may be pumped through theline 46 and through the port 47 into the cylinder 25 so as to move themember 19 vertically upwardly with respect to the mounting member 18.When the member 19 has been moved upwardly the desired distance, thevalve 44 may be adjusted so as to lock the member 19 in its adjustedposition. To lower the member 19, the valve 44 may be adjusted so as topermit fluid to drain from the cylinder 25, under the influence of theweight of the arm 19, into the reservoir 42 via the lines 46 and 45.

As is indicated in FIGURE 1 and in full lines in FIG- URE 6, the member19' projects forwardly of the base 1 so as to overlie the lapping wheel7. The longitudinal axis of the member 19 should lie on the diametralplane of the wheel 7 and to assure such a relationship when the member19 is in a lowered, operative position, the member 19 carries at itsrear end a guide and latch plate 47 that is adapted to fit snuglyagainst a companion abutment 48 that is carried by the support 17. Theplate 47 is adjustable vertically with the member 19 so as to beengageable with and disengageable from the abutment 48, and to assuresnug fitting of the parts without interference, the upper surface of theabutment 48 may be chamfered as at 49. To minimize the risk of injuringa workman, a three-sided guard 50 may extend around the parts 47 and 48and be secured to the support 17.

At the forward end of the arm member 19 is mounted a workpiece-engagingmember 51 comprising a disk or spider 52 of a diametral size such as tocorrespond substantially to the diametral size of the lapping wheel 7.The member 52 is provided with a plurality of circumferentially spacedopenings 53 (see FIGURE 8) having a configuration correspondingsubstantially to the configuration of a workpiece 54 that is adapted tobe accommodated therein.

Radially inwardly of each opening 53 is a mounting bracket 55 on whichis pivotally supported an angular arm 56 which, at its outer end,carries a presser plate 57. Each presser plate 57 is pivoted as at 58 toa ring 59 that is slideably and rotatably mounted on its associated arm56, thereby enabling the plate 57 to be substantially universallyadjustable. Each plate 57 is adapted to bear against a workpiece that isaccommodated in the associated opening 53 so as to press the workpieceagainst the upper surface of the lapping wheel 7. A verticallyadjustable stop 60 is associated with each arm 56 so as to limit theforce with which the plate 57 bears against the workpiece. Although onlytwo of the arms 56 and their associated devices are illustrated inFIGURE 1 for purposes of clarity, it will be understood that a largernumber of such devices may be utilized.

The workpiece-engaging member 52 i mounted on the supporting frame 19for rotation about an axis which may either coincide with the axis ofrotation of the lapping wheel 7 or which may move in an orbital pathabout the axis of rotation of the lapping wheel. The mounting means forthe workpiece-engaging member is best illustrated in FIGURES 2 and 3.The mounting means comprises a hollow support or carrier 62 that isrotatably journaled in the opening 20 of the arm member 19 by bearings63 and 64 for rotation about an axi that coincides with the axis ofrotation of the wheel 7. The lower end of the carrier 62 extends belowthe lower surface of the member 19 and is threaded to accommodate a nut65 which functions as a bearing retainer. The lower bearing 64 isprotected by a seal 66. As is best illustrated in FIGURES 2 and 3, thecarrier 62 has an eccentric bore 67 extending therethrough.

Rotatably mounted within the support 62 i a sleeve 68. The upper end ofthe sleeve 68 projects above the upper end of the carrier 62 and isprovided with an enlarged flange 69 in wedging relation with the upperend of the carrier 62. The lower end of the sleeve 68 extends below thelower end of the carrier 62 and is threaded to accommodate awedge-shaped locking nut 70 which may be adjusted so as selectively toenable and disable relative rotation of the carrier '62 and the sleeve68. The sleeve 68 also has an eccentric bore 71 extending completelythrough the sleeve, and the eccentricity of the bore 71 corresponds tothe eccentricity of the bore 67.

A spindle 72 is journaled for rotation about its own axis in the sleeve68 by means of bearings 73 and 74 and includes a lower, enlarged portion75 that extend below the sleeve 68 and is fixed to theworkpiece-engaging member 52. The upper end of the spindle 72 extendsabove the sleeve 68 for a purpose that hereinafter will be explained.

The apparatus includes means for rotating the members 62 and 68conjointly and comprises an electric motor 77 to the armature shaft ofwhich is fixed an adjustable diameter sheave 78 of known construction.The sheave 78 is connected by a belt 79 or the like to a similaradjustable diameter sheave 80 and which is fixed to a shaft 81 that isrotatably journaled in the arm member 19. Fixed to the shaft 81 is aworm 82 that meshes with a driving worm gear 83 which is fixed on thesupport or carrier 62. The adjustable diameter sheaves 78 and 80 havemanually operable adjusting knobs 84 and 85, respectively, by means ofwhich the diameters may be adjusted so as to vary the speed at which themembers 62 and 68 are rotated. Upon rotation of the worm 82, the gear 83rotates about a fixed axis and the carrier 62 rotates about the sameaxis. This axis coincides with the axis of rotation of the lapping wheel7 and is indicated in FIGURE 3 by the reference character X.

When the carrier 62 and the sleeve 68 are in the positions of adjustmentshown in FIGURES 2 and 3, the axis Y of rotation of the spindle 72 is inits maximum position of eccentricity to the axis X. Accordingly,rotation of the members 62 and 68 about the axis X will cause thespindle 72 to move in an orbital path about the axis X and such movementof the spindle 72 will cause the workpiece-holding disk 52 also to movein an orbital path about the axis of rotation of the lapping Wheel 7.

The eccentricities of the bores of the members 62 and 68 are such thatrotation of the member 68 relative to the carrier 62 through from theposition shown in FIGURE 3 will cause the axis Y of the spindle 72 tocoincide with the axis X. Such relative rotation of the members 62 and68 may be accomplished by loosening the nut 70. When the axes X and Ycoincide, rotation of the member 62 will cause corresponding rotation ofthe workholding disk 52 about the axis of rotation of the lapping wheel7. The members 62 and 68 may be so adjusted relatively to one another asto provide any desired degree of eccentricity of the axes X and Ybetween the maximum and zero eccentricities.

Apparatus constructed in accordance with the invention includes drivetransmitting means 86 for rotating the spindle 72 and the disk 52 aboutthe axis Y of the spindle, regardless of the eccentricity of the axes Xand Y. The drive transmitting means is located in a square, hollowhousing 87 having a bottom wall 88 fixed to the arm 19 and to which aresecured upstanding side walls 89. The

bottom wall 88 has an opening 90 therein which is coaxial with theopening 20. A cover 91 is removably secured to the walls 89.

The drive transmitting means 86 includes an intermediate planetary geartrain 92 comprising a sun gear 93 fixed to a block 94 that is secured tothe sleeve 68 for rotation with the latter. Both the gear 93 and theblock 94 loosely receive the spindle 72. The gear 93 is in mesh withthree idler gears 95 that are fixed on stub shafts 96 journaled in athree-armed spider member 97 that is keyed or otherwise suitably fixedto the upper end of the spindle 72. At the upper end of each shaft 96 issecured a gear 98 which meshes with the teeth 99 of an additional,ring-type gear 100. The body of the gear 100 is square in plan, but hasa size smaller than the interior size of the housing 87.

The gear 100 is slidably supported atop an open, square frame 101 thatis supported on a shelf 102 on the walls 89 so as to lie about midwaybetween the top and bottom walls of the housing 87. Slidably supportedon the frame 101 and overlying the gear 100 is a rectangular guide frame103 comprising two spaced apart, parallel bars 104 and 105 joined attheir opposite ends by bars 106 and 107. Each of the bars 104 and 105 isprovided with a downwardly projecting guide flange 108 between which isreceived the gear 100. Neither of the bars 106 and 107, however, isprovided with such a flange. Accordingly, the gear 100 is capable ofreciprocating movement between the guide flanges 108. The guide frame103 itself is slid able relatively to the housing 87, but in a directionnormal to the direction of sliding movement of the gear 100 relative tothe frame 103. The frame 103 is guided in its sliding movements by apair of guide surfaces 109 and 110 carried by the cover 91 at oppositeends thereof. As is indicated in FIGURE 2, the lower ends of the guides109 and 110 terminate at a level above the gear 100. The constructionand arrangement of the parts are such that, although the gear 100 isincapable of rotating about the axis of the spindle 72, it is capable ofsliding movements in either of two normal directions in the same planeand, therefore, is capable of moving orbitally about the axis X.

The drive transmitting means is so constructed that rotation of thecarrier member 62 is imparted via the sleeve member 68 to the sun gear93. Rotation of the sun gear 93 imparts rotation to the idler gears 95,and rotation of the gears 95 is imparted via the shafts 96 to theplanetary gears 98. Since the teeth of the planetary gears 98 mesh withthe teeth of the ring gear 100, and since the latter is restrainedagainst rotation by its engagement with the guides 108, 109 and 110,rotation of the gears 98 effects rotation of the spider member 97 and,consequently, rotation of the spindle 72 about its own axis Y. The speedof rotation of the spindle 72 about its own axis will depend on theratio of the gears in the drive transmitting mechanism, the speed of thedriving motor 78 and the ratio between the diameters of the pulleys 78and 80, but the member 62 should be rotated several times the speed ofrotation of the spindle 72.

When the apparatus is conditioned for operation, the frame member 19will be in the position shown in FIG- URE 1 and in full lines in FIGURE6 so that the axis X coincides with the axis of rotation of the lappingwheel 7. This relationship is assured by the cooperating latch parts 47and 48. The handwheel 38 may be so adjusted as to locate theworkpiece-carrying disk 52 at the desired clearance above the uppersurface of the lapping wheel. The motors 8 and 77 then may be started soas to effect concurrent rotation of the lapping wheel 7 and theworkpiececarrying member 52 in opposite directions and at differentspeeds.

When the members 7 and 52 attain the desired speeds of rotation,workpieces 54 may be inserted in the cavities 53 of the member 52 so asto locate the lower surface of each such workpiece in engagement withthe upper surface of the lapping wheel. To facilitate introduction andremoval of workpieces to the cavities 53, each of the arms 56 may beprovided with a radially inner extension 111 which lies in the path of acam 112 supported at the forward end of the arm member 19 and whichcooperates with the extension 111 to lift momentarily the presser plate57 so as to permit access to the cavity 53.

If the carrier member 62 and the sleeve 68 are so adjusted relatively toone another that the axis Y of the spindle 72 coincides with the axis Xof the member 62, each workpiece 54 will be moved in a circular pathabout the axis of rotation of the lapping wheel 7. It is preferred,however, to adjust the members 62 and 68 in such manner that eachworkpiece 54 will move in a circuitous path about the axis of thelapping wheel.

When the members 62 and 68 are in their maximum positions ofeccentricity, as is indicated in FIGURES 2 and 3, operation of theapparatus will cause a workpiece 54 to traverse an orbital path aboutthe axis of rotation of thelapping wheel 7. Thus, as is indicated inFIGURE 8, each workpiece 54 will traverse the surface of the lappingwheel along a path in the form of a sine Wave so that each workpiecemoves first radially outwardly and then radially inwardly of the wheel7, simultaneously with its movement circumferentially of the wheel. Theamplitude of radial movement of each workpiece relative to the lappingwheel may be adjusted by adjustment of the eccentricity of the axes Xand Y, and the number of cycles of such movement will depend upon. thedifference in speeds of rotation of the carrier 62 and theworkpiececarrying member 52. Inasmuch as the speed of rotation of eitheror both of the members 62 and 52 may be adjusted, the relative speed maybe selected to provide the best results for the particular workpiecesbeing lapped.

When it becomes necessary to dress. the upper surface of the lappingwheel 7, the hydraulic pump 41 may be started and the valve 44 adjustedso as to introduce pressure fluid to the chamber between the plate 26and the upper end of the mounting tube 18, thereby effecting upwarddisplacement of the arm member 19 relative to the base 1. When the armmember 19 has been adjusted to a height such that the workpiece-carryingmember 52 may clear the shield 16, the latch members 47 and 48 will bedisengaged, whereupon the arm member 19 may be swung about the axis ofthe tube 18, as is indicated in dotted lines in FIGURE 6. A wheeldresser (not shown) then may be utilized to resurface the dressingwheel.

Following the dressing of the lapping wheel, the arm member 19 may beswung back to its original position and the valve 44 adjusted to permitthe arm member to return to its lowered, operative position, whereuponthe latch members 47 and 48 will latch the arm in the previouslydescribed position. In the event it becomes necessary to make a furthervertical adjustment of the workpiececarrying member 52 such as tocompensate for the removal of material from the lapping wheel, thehandwheel 38 may be rotated in the appropriate direction.

The disclosed apparatus and methods are representative of presentlypreferred forms of the invention, but are intended to be illustrativerather than definitive thereof. The invention is defined in the claims.

I claim:

1. A machine tool construction comprising supporting frame means;carrier means mounted on said frame means for rotation about an axis;drive means connected to said carrier means for rotating the latterabout said axis; sleeve means eccentric to said axis carried by saidcarrier means for rotation about said axis in response to rotation ofsaid carrier means; spindle means; means journaling said spindle meanson said sleeve means for rotation relative thereto about the axis ofsaid spindle means; and rotatable and bodily displaceable gear meansdrivingly interconnecting said sleeve means and said spindle means forrotating said spindle means about its own axis in response to rotationof said carrier means about its said axis, whereby said spindle means isenabled to move in an orbital path about the axis of said carrier means.

2. The construction set forth in claim 1 wherein said eccentric means isadjustable relatively to the axis of said carrier means; and includingmeans for maintaining said eccentric means in a selected position ofadjustment relative to said axis.

3. The construction set forth in claim 2 wherein said eccentric means isadjustable relatively to the axis of said carrier means from a positionin which the axis of said spindle means coincides with the axis of saidcarrier means to a position in which said axes are spaced from oneanother.

4. Apparatus for use with a lapping machine having an annular grindingwheel presenting a fiat face of predetermined radial width, and meansfor rotating said wheel about an axis, said apparatus comprisingsupporting frame means; a tubular carrier member having an eccentricbore therethrough; means mounting said carrier member on said framemeans for rotation about an axis coincident with the axis of said wheeland eccentric to said bore; drive means connected to said carrier memberfor rotating the latter about said axis; a sleeve member rotatablysupported within the bore of said carrier member and having an eccentricbore therein complementary to the bore of said carrier member; a spindlerotatably mounted within said sleeve member for rotation about its ownaxis; means on said spindle for holding a workpiece against said face ofsaid wheel; adjustable means reacting between said carrier member andsaid sleeve member for maintaining said members in a selected positionof relative angular adjustment between a first position in which theaxis of said spindle coincides with the axis of said carrier member andanother position in which the axis of said spindle is spaced from theaxis of said carrier member; and drive transmitting meansinterconnecting said carrier member and said spindle for rotating thelatter about its own axis solely in response to rotation of said carriermember.

5. The apparatus set forth in claim 4 wherein said drive transmittingmeans comprises a planetary gear train.

6. The apparatus set forth in claim 5 wherein said planetary gear traincomprises a sun gear on said carrier member, planetary gearing on saidspindle, and ring gear means on said frame, said planetary gearing beingin mesh with said sun gear and with said ring gear means.

7. The apparatus set forth in claim 6 wherein said ring gear means ismovable relatively to said spindle in either of two mutually normaldirections in the same plane.

8. Driving apparatus comprising driving gear means; means mounting saidgear means for rotation about a fixed axis; a spindle; means mountingsaid spindle for rotation about said fixed axis and about its own axis;intermediate gear means in mesh with said driving gear means; anadditional gear means in mesh with said intermediate gear means; meansmounting said additional gear means to preclude rotation thereof and toenable linear movements thereof in either of two mutually normaldirections in substantially the same plane; and means connecting saidintermediate gear means to said spindle for rotating the latter aboutits said own axis in response to rotation of said driving gear meansabout said fixed axis.

9. The apparatus set forth in claim 8 wherein said spindle is mountedeccentrically of said fixed axis.

10. The apparatus set forth in claim 8 wherein the mounting means forsaid spindle is adjustable relatively to said driving gear means foradjusting said spindle from a position in which said axes coincide to aposition in which said axes are spaced apart.

11. Driving apparatus comprising driving gear means rotatable about anaxis; driven gear means in mesh with said driving gear means and adaptedto be driven by the latter; linearly displaceable and nonrotatable gearmeans in mesh with said driven gear means; and rotatable means connectedto said driven gear means for rotation in response to driving of saiddriven gear means by said driving gear means.

12. The apparatus set forth in claim 11 wherein said rotatable meanscomprises a spindle; and means mounting said spindle for rotation aboutits ownaxis and for rotation about the axis of said driving gear means.

13. The apparatus set forth in claim 11 wherein said nonrotatable gearmeans is movable in two mutually normal directions in the same plane.

14. A method of lapping a workpiece comprising holding a workpieceagainst a lapping wheel having an annular surface; moving said workpiecein a circumferential path relatively to said wheel; and sequentiallymoving said workpiece radially at a uniform rate inwardly and outwardlyrelatively to said wheel as said workpiece is moved in said path andwith such frequency and amplitude that said workpiece traverses asinusoidal path about said lapping wheel.

15. A machine tool construction comprising a lapping wheel; meansmounting said wheel for rotation about a first axis; support means forholding a workpiece against said wheel; means for rotating said supportmeans about a second axis parallel to said first axis; means mountingsaid support means for movement toward and away from said wheel and forrotary movements relative to said wheel about a third axis parallel tosaid second axis for moving the axis of rotation of said support meansinto and out of a fixed predetermined relationship with said first axis;and releasable latch means acting on said support means in response tomovement thereof toward said wheel when said support means is in saidpredetermined relationship for releasably maintaining said support meansfixed in said relationship relative to said axis.

16. A machine tool construction comprising a lapping wheel; meansmounting said wheel for rotation about a first axis; support means forholding a workpiece against said wheel; arm means mounting said supportmeans for rotation about a second axis; means mounting said arm meansfor movements toward and away from said wheel and for rotation about athird axis to and from a fixed position in which said first and secondaxes are coincident, said third axis being parallel to said first axis;and releasable latch means on said arm means operable in response tomovement thereof toward said wheel to latch said arm means in said fixedposition and operable in response to movement of said means away fromsaid wheel to release said arm means.

17. The construction set forth in claim 16 including means connected tosaid arm means and operable to effect movement of said support meanstoward and away from said wheel.

References Cited UNITED STATES PATENTS 2,225,826 12/1940 Duifens 511241,151,785 8/1915 Hitchcock 5l133 1,561,107 11/1925 Parsons 51-1331,577,137 3/1926 Maynard 51-133 1,610,527 12/1926 Indge 51133 1,739,9618/1929 Wentz 51-131 X 1,874,920 8/1932 Dehufl.

2,272,974 2/ 1942 Indge 51120 2,740,237 4/1956 Day 51-120 X 3,172,2413/1965 Habenicht 51120 HAROLD D. WHITEHEAD, Primary Examiner US. Cl.X.R.

